Coal mining or augering machines operated by internal combustion engines have been employed for mining coal from outside a hill containing a coal seam, whereby a high percentage of the outcropping coal is removed. These mining machines usually include an auger having a cutting head which is advanced longitudinally into the seam during the mining operation to a depth of approximately two hundred feet to form a cylindrical hole in the coal seam. The auger, which is usually made up of a series of auger sections, detachably connected end-to-end, conveys the cut coal to a point of discharge outside the seam.
To increase the yield of a given seam, multiple cutting heads have been employed to form a series of parallel, cylindrical holes in the coal seam, whereby a large amount of coal remains in place in the seam because the shape of the holes leaves thick webs between the holes. To further increase the yield of the seam, it has been proposed to construct and arrange a plurality of cutting heads in such a manner to form a hole having a substantially square cross-section.
While these coal mining machines have been satisfactory for their intended purpose, they have been characterized by being quite large and thus difficult to control for changing the direction of the holes. These machines are also expensive and thus unaffordable by the small coal operator.